Question

Rex's puppy is 5 years younger than his other dog. If the other dog is x years old, what is an expression for the puppy's age?

Answer 1

The other dog's age is "x". Rex's puppy is 5 years less than "x". SO...
x-5.

Understand?

Answer 2

X -- 5=.
X is the variable.
-- is the operation.
5 is the puppy's age